1. Field of the Invention
The present invention relates to a magnetic disk drive which is used as an external storage unit of a computer.
2. Description of the Related Art
FIG. 8 is a perspective view of an example of a conventional magnetic disk apparatuses, which is shown in a catalogue of a microfloppy disk drive (3.5-inch flexible disk drive: MP-F11W) produced by SONY Corporation. This is a very general 3.5-inch flexible disk device (hereinunder referred to as "FDD"). In FIG. 8, the reference numeral 1 represents a magnetic head, 2 an arm to which the magnetic head 1 is fixed such that the magnetic head 1 exists within a predetermined azimuth, 3 a carriage to which the magnetic head 1 on the opposite side is fixed such that the magnetic head 1 exists within a predetermined azimuth, 4 a pressure spring for applying a predetermined pressure to the magnetic head 1 through the arm 2, 5 a metal fitting for fixing the pressure spring 4 to the carriage 3, 6 a lead screw which axially rotates and induces the linear reciprocal movements of the carriage 3, 7 a stepping motor for applying a driving force to the lead screw 6, and 8 a flexible printed circuit (hereinunder referred to as "FPC").
The reference numeral 9 denotes a loading mechanism having a function of mounting and removing a cartridge which is shown in FIG. 9, 10 a base to which various structures are fixed so as to be accommodated therein, 11 a front panel which is attached to the front surface of the disk drive, 12 a door provided on the front panel 11 so as to be opened and closed when the cartridge 18 is mounted or removed, 13 a push button which is pressed into the apparatus or released coupled with the movement of the loading mechanism 9, 14 a printed circuit board which is fixed to the bottom portion of the base 10, and 15 a mounting frame for mounting the drive on a system such as a personal computer.
FIG. 9 is a perspective view of the cartridge 18. The reference numeral 16 represents a flexible recording medium on and from which information is written or read by the magnetic heads 1, 17 a shutter which is opened or closed coupled with the movement of the loading mechanism 9 so as to expose or cover the portion of the recording medium 16 with which the magnetic head 1 comes into contact, 19 a chucking plate magnetically attracted to the rotary portion of a spindle motor (not shown) which is provided in the disk drive shown in FIG. 8, 20 a center hole for receiving the centering shaft of the spindle motor and 21 a driving hole into which the driving pin of the spindle motor is inserted and to which the driving force is transmitted.
FIG. 10 is a plan view of another conventional magnetic disk drive shown in International Publication No. W089/08313. This is a typical 2.5-inch fixed disk drive. In FIG. 10, the reference numeral 108 represents an FPC, 110 a base, 122 a hard recording medium using an aluminum alloy as a base material, 123 a magnetic head for writing and reading information while floating above the recording medium 122 with a minute space therebetween, 124 a suspension made of an SUS spring material which is pivotally supported by the upper portion of the magnetic head 123, 125 an actuator to which the suspension 124 is fixed and which rocks the magnetic head 123 approximately in the radial direction above the recording medium 122, 126 a pivot as the center axis of the rocking movement of the actuator 125, 127 a coil bobbin which is fixed to the actuator 125 at the end opposite to the end to which the suspension 124 is fixed, 128 a magnet which vertically sandwiches the coil bobbin 127 with a minute space therebetween, and 129 a ramp loading mechanism which comes into contact with the suspension 124 and holds the magnetic head 123 with a predetermined distance from the recording medium 122 when the magnetic head 123 moves outside of the recording medium 122.
FIG. 11A is a side elevational view of the disk drive shown in FIG. 10. The reference numeral 141 represents a printed circuit board, 130 a cover which is bonded to the base 110 shown in FIG. 10 so as to seal the disk drive, and 131 a rubber cushion which is attached to the bottom surface of the base 110 so as to mitigate the vibration and the shock of the disk drive.
The operations of these conventional magnetic disk drives will now be explained. An FDD, which is the conventional magnetic disk drive shown in FIG. 8, will first be explained. When the cartridge 18 shown in FIG. 9 is inserted from the door 12 of the front panel 11, the shutter 17 is slid in the direction indicated by the arrow A in FIG. 9 by the loading mechanism 9, thereby exposing the portion with which the magnetic head 1 comes into contact. At the same time, the chucking plate 19 is attracted to the spindle chucking surface by the magnetic force of a magnet provided on the spindle chucking surface.
The push button 13 projects coupled with the movement of the loading mechanism 9. The arm 2 is pushed down by the pressure spring 4 and the magnetic head 1 fixed on the arm 2 comes into contact with the recording medium 16, whereby the recording medium 16 is sandwiched between the magnetic head 1 fixed on the arm and the magnetic head 1 fixed on the carriage 3. When the recording medium 16 is normally chucked, the spindle motor starts to rotate, and the driving pin of the spindle motor comes into the driving hole 21 provided in the chucking plate 19, so that the recording medium 16 also rotates. The rotation of the stepping motor 7 is transmitted to the carriage 3 through the lead screw 6 and the carriage 3 linearly reciprocates by the distance which is proportional to the rotational angle of the stepping motor 7, so that the magnetic head 1 is positioned at the desired track position of the recording medium 16 in accordance with the command from the system.
When the positioning of the magnetic head 1 is finished, the magnetic head 1 starts to write or read information on or from the magnetic recording medium 16. When the user presses the push button 13 in order to take out the cartridge 18 after the end of the writing/reading of necessary information, the loading mechanism 9 operates the other way around. That is, the arm 2 is pushed up, and the cartridge 18 is pushed out of the door 12 of the front panel 11. This FDD operates in the same way with respect to any other recording medium 16. In addition, in order to enable the recording medium 16 to operate normally in any other disk drive, namely, to impart compatibility between drives to the recording medium 16, the magnetic head 1 is fixed to the arm 2 within a predetermined azimuth in any disk drive.
The operation of a fixed disk drive (HDD), which is the other conventional magnetic disk drive shown in FIG. 10, will now be explained. The hard recording medium 122 produced by applying, plating or sputtering a magnetic material on a base of an aluminum alloy is rotated at a high speed, and the magnetic head 123 is positioned at the desired track of the recording medium 122 in accordance with the command from the system while floating thereabove at a minute height of the submicron order for writing or reading information. At this time, the actuator 125 for moving the magnetic head 123 is rocked around the pivot 126 by the rotational force produced by the electromagnetic induction between the magnet 128 and the coil bobbin 127. In this way, since the structure composed of the magnetic head 123, the suspension 124, the actuator 125 and the coil bobbin 127 has the center of the moment of inertia in the vicinity of the pivot 126 and the magnetic head 123 is floating above the recording medium 122, the frictional resistance is small. In addition, since a ball bearing is used for the pivot 126, the rotational frictional resistance is small. For these reasons, it is possible to rock the magnetic head 123 at a high speed.
In this HDD, it is possible to slightly move and position the magnetic head 123 by the servo information which is written in the recording medium 122 in advance and the function of the printed circuit board 141. As a result, it is possible to increase the number of tracks, thereby realizing high-density high-capacity recording. In addition, when the magnetic head 123 is not used for writing/reading for a long time or when the power source is off, the actuator 125 is moved to the outer peripheral side and the suspension 124 is mounted on the ramp loading mechanism 129, thereby keeping the magnetic head 123 at a predetermined position outside of the recording medium 122.
In this way, it is possible to reduce the consumption power and prevent the recording medium 122 from being damaged due to the tapping of the magnetic head 123 on the recording medium 122 while the disk drive is not operated. As described above, since the magnetic head 123 floats above the recording medium 122 at a height of the submicron order, it is necessary to prevent the ingress of dust from the outside in order to realize accurate operation of the apparatus. For this purpose, the cover 130 is bonded to the base 110 through a gasket so as to seal the disk drive.
An FDD as a conventional magnetic disk drive in which a recording medium is replaceable has the above-described structure. Such an FDD must be free from the non-uniformity in the chucking accuracy at which a recording medium is chucked by the spindle and the non-uniformity in the rotational accuracy due to the non-uniformity in the chucking accuracy so as to write and read information on and from any recording medium in the same way. For this reason, the FDD must have a compatibility between recording mediums and impart a compatibility between drives to a recording medium. If these demands are satisfied, the increase in the recording density is checked and it is difficult to reduce the size of the disk drive in spite of a small capacity. In addition, since the disk drive does not have a sealed structure so as to make a recording medium replaceable, the dust which has entered the apparatus goes between the magnetic head and the recording medium and damages the recording medium or adheres to the driving mechanism such as the lead screw, thereby deteriorating the positioning accuracy and lowering the reliability.
On the other hand, the fixed disk drive as another conventional magnetic disk drive can have a sealed structure because the recording medium is not replaceable. However, various elements such as a spindle motor driving mechanism and an actuator driving mechanism are accommodated in the sealed container, the disk drive as a whole becomes inconveniently large.